Clown loach

Quick facts

Adult size

30 cm

Lifespan

can live up to 25 years; very long-lived; oldest documented over 20 years, hobby specimens routinely 15-20

Tank zone

bottom

Temperament

peaceful

Difficulty

intermediate

Schooling

recommended 5+ (critical minimum 4, thrives at 8+)

Typically wild-caught

yes - acclimate slowly

Water parameters

Temperature

25–30°C

pH

5.5 to 7.5

Hardness

1 to 12 dGH

Tank requirements

Minimum volume

450 L

Minimum length

180 cm

Flow

moderate

Lighting

dim preferred

Substrate

sand

Driftwood

preferred

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: omnivore, feeds primarily at the bottom.

Omnivore with a strong preference for meaty food. Sinking pellets, algae wafers, frozen bloodworm, frozen brine shrimp, frozen mysis, and live food (blackworms, earthworm pieces) are all taken eagerly. They love snails and will systematically clear a tank of pest snails within days. Vegetable matter is accepted too: blanched zucchini, cucumber, and peas. Feed sinking food that reaches the bottom before midwater fish intercept it. Clown loaches are greedy but slow to start feeding; they hang back until the initial frenzy dies down, then methodically work over the substrate. Feed once or twice daily. Larger specimens need substantial portions; a group of five adults at 20 cm eats a lot of food.

Vegetable matter required (algae wafers, blanched zucchini, spinach).

Compatibility

• Social fish that must be kept in groups. A solitary clown loach is a stressed clown loach: it hides constantly, loses color, and often refuses food. Groups of 5+ show natural behavior, including their signature habit of lying on their sides, which panics new owners into thinking the fish is dead.
• Peaceful toward tankmates of all sizes. Despite reaching 25–30 cm, they're not predatory toward fish (though small shrimp disappear). Good companions for medium to large community fish: rainbowfish, larger tetras, barbs, other loaches, and non-aggressive cichlids.
• Snail exterminators. Clown loaches eat every snail they can extract from a shell. Pest snails, mystery snails, nerites, assassin snails; none survive. This is useful if you have a snail problem and catastrophic if you're keeping ornamental snails on purpose.
• The most mis-sold fish in the hobby. Stores sell 5 cm juveniles to people with 75-liter tanks. The fish reaches 25–30 cm over several years and needs 450 L as an adult group. Many end up stunted, stressed, and prone to disease in tanks that are far too small.

Habitat

Native to fast-flowing rivers in Sumatra and Borneo, Indonesia. Wild habitat is warm (25–30°C), well-oxygenated water with moderate to strong current over rocky and sandy substrates. The fish is found in clear-water rivers, not blackwater streams. During the breeding season, adults migrate upstream into smaller tributaries and flooded forest areas. The orange body with three bold black vertical bars is one of the most recognizable color patterns in the freshwater hobby. Juveniles are more vivid; adults develop a deeper, more muted orange. The species (Chromobotia macracanthus) has a suborbital spine below each eye that can be erected when the fish is stressed or handled. These spines catch on nets and can puncture bags, so use a rigid container when moving them. Clown loaches are among the longest-lived aquarium fish: verified reports exist of specimens over 25 years old, and 15-20 years is common in good conditions. Growth is slow but steady; they can take 5-8 years to reach full adult size. All specimens in the trade are either wild-caught from Indonesian rivers or commercially bred in large outdoor ponds using hormone injection. No hobbyist has reliably bred them at home.

Breeding

Not bred in home aquariums. Every attempt documented in the hobby literature has failed. The species requires specific seasonal triggers (monsoon flooding, upstream migration, temperature and pressure changes) that can't be replicated in a glass tank. Sexing is unreliable; females may be slightly plumper but the difference is subtle and inconsistent. Commercial operations in Southeast Asia breed them in large earthen ponds using hormone injections (typically HCG or pituitary extract) to induce spawning. The details of these operations are not widely published. Wild-caught fish from Borneo and Sumatra make up a significant portion of the trade, and there are periodic conservation concerns about overharvesting, especially of juveniles. Captive-bred stock from farms is increasingly available and generally hardier than wild-caught specimens.

Common problems

Ich susceptibility is the defining health concern. Clown loaches contract ich more readily than almost any other freshwater species. After purchase, during temperature drops, or when stressed by transport, ich outbreaks are nearly inevitable. Treatment is complicated by the fact that they're scaleless and sensitive to standard medication doses. Heat treatment (raise to 30°C for 10-14 days) is the safest approach. If medication is necessary, use half the recommended dose. Malachite green and formalin at full strength can kill them. The growth-versus-tank-size mismatch is the other major problem. A group of clown loaches in a 100-liter tank will seem fine for a year or two, then growth stalls, colors fade, and health problems multiply. They need 450 L for a group of adults, with strong filtration and good current. Lying on their side (the 'playing dead' behavior) is normal for this species and not a sign of illness, but it triggers panic in keepers who aren't expecting it.

Bioload

Bioload coefficient: 6.5 (large active loach, high foraging activity; comparable per-cm to a goldfish).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size